1. Field of the Invention
An embodiment of the present invention relates to a scintillator array, and an X-ray detector and an X-ray examination device using the scintillator array.
2. Description of Related Art
In fields of medical diagnosis and industrial nondestructive inspection, an X-ray examination device such as an X-ray tomographic photographing device (X-ray CT device) is used. The X-ray CT device has a structure in which an X-ray tube (X-ray source) that radiates fan beam X-rays in a fan shape and an X-ray detector composed of many X-ray detecting elements arranged in parallel are arranged to be opposed to each other with a tomographic surface of a specimen as a center. In the X-ray CT device, the fan beam X-rays are radiated from the X-ray tube to the specimen, and X-ray absorption data transmitted through the specimen is collected by the X-ray detector. The X-ray absorption data collected by the X-ray detector is analyzed by a computer. Concretely, calculation of an X-ray absorptance at individual position in the tomographic surface and reconfiguration of an image according to the X-ray absorptance are performed. Thus, a tomogram of the specimen is reproduced.
As the X-ray detector of the X-ray CT device, a detector having a solid scintillator that emits visible light by excitation with X-rays is frequently used. In the X-ray detector using the solid scintillator, it is easy to increase the number of channels by downsizing the X-ray detecting element, and the resolution of the X-ray CT device can further be increased. Various materials are known as the solid scintillator, and a ceramics scintillator composed of a sintered compact of rare earth oxysulfide such as Gd2O2S:Pr is particularly effective. The ceramics scintillator composed of the sintered compact of rare earth oxysulfide is excellent in emission efficiency because of large X-ray absorption coefficient and is suitable as a scintillator for X-ray detector because of short afterglow.
For the sintered compact of rare earth oxysulfide phosphor (phosphor ceramics) constituting the ceramics scintillator, various suggestions have been made to improve the optical output, increase the density of the sintered compact, improve the mechanical strength and so on. For example, the optical output is improved by controlling the phosphor amount in the ceramics scintillator (sintered compact). However, the ceramics scintillator is required to further improve optical output. The improvement in optical output of the scintillator leads to a reduced examination time by the X-ray examination device, namely, reduced radiation exposure. To improve the optical output, improvement of a scintillator material can be effective means. Further, in the case where an array structure in which a reflective layer interposed between adjacent scintillator blocks is applied to the ceramics scintillator, improvement of the reflective layer can also be effective means for improving the optical output.
As a conventional scintillator array, there is a known structure in which a radiation shielding plate is interposed between adjacent scintillator blocks and the scintillator blocks are bonded to the radiation shielding plate with an adhesive layer containing titanium oxide powder. The radiation shielding plate and the adhesive layer interposed between the scintillator blocks contribute to the improvement in reflection efficiency of visible light emitted from the scintillator blocks. However, in the case of using both of the radiation shielding plate and the adhesive layer containing titanium oxide powder, an increase in manufacturing cost of the scintillator array is inevitable. Further, in the adhesive layer bonding the scintillator blocks to the radiation shielding plate, fine particles having a mean particle diameter of 1 μm or less are used as the titanium oxide powder. The titanium oxide in a fine particle form is likely to aggregate in the adhesive layer, thereby decreasing the reflection efficiency of the adhesive layer. Also from the point, the radiation shielding plate is used in the conventional scintillator array.